import type { IUptimeRunnerConfig } from './interfaces.ts';

export const DEFAULT_CONFIG_PATH = '/etc/uptimerunner/config.json';

export async function loadConfig(configPathArg = getConfigPath()): Promise<IUptimeRunnerConfig> {
  const fileConfig = await readConfigFile(configPathArg);
  const config = applyEnvironmentOverrides(fileConfig);
  validateConfig(config);
  return config;
}

export async function writeConfig(
  configArg: IUptimeRunnerConfig,
  configPathArg = getConfigPath(),
): Promise<void> {
  validateConfig(configArg);
  const configDir = configPathArg.slice(0, configPathArg.lastIndexOf('/')) || '.';
  await Deno.mkdir(configDir, { recursive: true });
  await Deno.writeTextFile(`${configPathArg}.tmp`, `${JSON.stringify(configArg, null, 2)}\n`);
  await Deno.rename(`${configPathArg}.tmp`, configPathArg);
}

export function getConfigPath(): string {
  return Deno.env.get('UPTIMERUNNER_CONFIG') || DEFAULT_CONFIG_PATH;
}

export function applyEnvironmentOverrides(configArg: Partial<IUptimeRunnerConfig>) {
  const labels = Deno.env.get('UPTIMERUNNER_LABELS');
  const pollIntervalMs = Deno.env.get('UPTIMERUNNER_POLL_INTERVAL_MS');
  const maxConcurrentChecks = Deno.env.get('UPTIMERUNNER_MAX_CONCURRENT_CHECKS');

  return {
    ...configArg,
    instanceUrl: Deno.env.get('UPTIMERUNNER_INSTANCE_URL') || configArg.instanceUrl,
    runnerId: Deno.env.get('UPTIMERUNNER_RUNNER_ID') || configArg.runnerId,
    token: Deno.env.get('UPTIMERUNNER_TOKEN') || configArg.token,
    labels: labels
      ? labels.split(',').map((labelArg) => labelArg.trim()).filter(Boolean)
      : configArg.labels,
    pollIntervalMs: pollIntervalMs ? Number(pollIntervalMs) : configArg.pollIntervalMs,
    maxConcurrentChecks: maxConcurrentChecks
      ? Number(maxConcurrentChecks)
      : configArg.maxConcurrentChecks,
  } satisfies Partial<IUptimeRunnerConfig>;
}

export function validateConfig(
  configArg: Partial<IUptimeRunnerConfig>,
): asserts configArg is IUptimeRunnerConfig {
  if (!configArg.instanceUrl) {
    throw new Error('Missing instanceUrl. Set it in config or UPTIMERUNNER_INSTANCE_URL.');
  }
  if (!configArg.runnerId) {
    throw new Error('Missing runnerId. Set it in config or UPTIMERUNNER_RUNNER_ID.');
  }
  if (!configArg.token) {
    throw new Error('Missing token. Set it in config or UPTIMERUNNER_TOKEN.');
  }
  if (configArg.pollIntervalMs !== undefined && configArg.pollIntervalMs < 1000) {
    throw new Error('pollIntervalMs must be at least 1000ms.');
  }
  if (configArg.maxConcurrentChecks !== undefined && configArg.maxConcurrentChecks < 1) {
    throw new Error('maxConcurrentChecks must be at least 1.');
  }
}

async function readConfigFile(configPathArg: string): Promise<Partial<IUptimeRunnerConfig>> {
  try {
    const configText = await Deno.readTextFile(configPathArg);
    return JSON.parse(configText) as Partial<IUptimeRunnerConfig>;
  } catch (error) {
    if (error instanceof Deno.errors.NotFound) {
      return {};
    }
    throw error;
  }
}